部分相干平顶激光组束投射腔壁光强的分布特性

Intensity Distribution Characteristics of Partially Coherent Flat-Topped Beam Combination Projected on Cavity Wall

建立了间接驱动过程中激光组束通过透镜在黑腔柱体中传输的模型。利用柯林斯公式,将各个锥环所有激光束投射到腔壁上的所有焦斑光强进行非相干叠加,研究其光强分布。详细分析了空间相干度、透镜聚焦F数、离焦距离对靶壁上焦斑光强分布均匀性的影响。空间相干度增大时,非相干叠加得到的亮斑光强度增大,光强起伏更剧烈,顶部光强分布均匀性变差;增大透镜聚焦F数,焦斑光场增强,光强振荡程度加深,光场分布更不均匀;而离焦量变大时,靶腔壁上的光强度降低,其振荡程度也减弱,光强峰值差值变小,顶部光强分布变得均匀。

A model is established to study the propagation of the lens-focused laser beam combination in the hohlraum in the progress of laser indirect driving. As for all laser beams in cone rings projected on the hohlraum wall,the incoherent superposition characteristics of intensity distribution of focal spots are investigated based on the Collins formula. The effects of relative spatial coherence degree, lens focusing F number and defocusing amount on the intensity distribution uniformity of focal spots projected on the target wall are discussed in detail. As the spatial coherence degree increases, the spot intensity of incoherent superposition increases, the light intensity fluctuation becomes more apparent, and the uniformity of the top light intensity distribution deteriorates. The spot intensity also increases with the increase of focusing F number, the intensity fluctuation is more violent, and the uniformity of the top light intensity distribution deteriorates. As the defocusing amount increases, the light intensity on the target chamber surface is reduced, the volatility degree and the difference of light intensity peak are smaller while the top intensity distribution becomes more homogenous.